1. Field of the Invention
The invention relates in general to a touch control system, and more particularly, to a technique for enhancing the accuracy when sensing results at border regions of a touch panel.
2. Description of the Related Art
Operating interfaces of recent electronic products are becoming increasingly user-friendly and intuitive. For example, through a touch screen, a user can directly interact with applications as well as input messages/texts/patterns with fingers or a stylus, thus eliminating prior complications associated with other input devices such as a keyboard or buttons. In practice, a touch screen usually includes a touch panel and a physical display disposed at the back of the touch panel. According to a touch position on the touch panel and a currently displayed image on the display, an electronic device determines an intention of the touch to execute corresponding operations.
Existing capacitive touch sensing techniques may be roughly categorized into self-capacitive and mutual-capacitive types. Compared to mutual-capacitive touch panels, self-capacitive touch panels can be implemented with single-layer electrodes having a simpler manufacturing process and lower cost, and thus generally prevail in many entry-level electronic products. FIG. 1A shows an example of a conventional self-capacitive touch panel known in the prior art. In a sensing area 100 demarcated by a dotted frame, multiple triangular electrodes (e.g., electrodes E1 and E3) and multiple rhombus electrodes (e.g., electrodes E2, E4, and E5) are disposed. Each of the electrodes in the diagram is connected to a sensor (not shown). When a user touching a region of the electrode E2, for example, the sensor connected to the electrode E2 senses a capacitance change in the electrode E2. A subsequent control circuit may then accordingly determine that the user touches the region of the electrode E2.
In the above example, the sensors are disposed outside the sensing area 100. FIG. 1B shows an example of a conventional wiring arrangement. As shown in FIG. 1B, with respect to electrodes at a border of the sensing area, e.g., the electrodes E1 and E2, a connecting wire 11 for connecting the electrode E1 to a sensor and a connecting wire 12 for connecting the electrode E2 to a sensor can both directly connect to the corresponding sensors. In contrast, a connecting wire 13 for connecting the electrode E5 to a sensor includes several segments. More specifically, the connecting wire 13 first passes through a gap between the electrodes E2 and E4 and then a gap between the electrodes E2 and E5 to connect to the corresponding sensor. It can thus be appreciated that, to all electrodes that are not adjacent to borders of the sensing area 100 (e.g., the electrodes E4 and E5), the connecting wires must detour around various electrodes (potentially a relatively large number) to eventually connect to sensors located outside the sensing area 100.
In practice, to optimize a sensing resolution, a narrower gap between two adjacent electrodes is preferred. The above arrangement, in which connecting wires need to pass through one or several gaps, inevitably enlarges the gaps between the electrodes. In certain cases, some gaps even grow wider to accommodate the passing of several connecting wires. Since the connecting wires passing through the narrow gaps need masking in the manufacturing process, production costs of the touch panel is thus significantly increased.
Moreover, since the connecting wires are usually made of metal materials easily affected by user touch, the connecting wires passing through the gaps may lead the control circuit to misjudge an actual user touch position. For example, when a user touch takes place between the electrodes E2 and E4, the connecting wire 13 passing through the gap between the electrodes E2 and E4 is also affected, such that the sensor connected to the electrode E5 also senses the corresponding capacitance change. When a sensing result of the sensor connected to the electrode E5 is taken into consideration in determining a touch position, an obvious error may occur in the touch position determined by the control circuit.